Best way to avoid this hunchback look when unloaded is to attach the fender to the swing arm with struts, and make it a "hugger".
I'm actually having someone fab up some struts for me now for just this purpose. Some local cops decided my no-rear-fender setup was a reason to threaten impoundment of my bike, and this is the easiest way to install one while retaining my cafe-dirt track tail section thing.
Trimming my former drum brake front fender to just nestle in behind the swingarm axle, to be held in place for now with a hose clamp passing through a slit in the fender. (yes, I am a ghetto engineer.)
Struts to run from the rear shock mounts to bolt holes on the fender. It's a temporary thing, I think, for now. But certainly seemed easier than mounting it to the frame. It's a bit more unsprung weight but don't think it'll destroy my otherwise-highly-tuned rear suspension action...
All in all, in flat black it is as close to a no-rear-fender look as I could get, and if you paint it something pretty it'll look very nice. It's easily trimmed to whatever length you like.